WASH­ING­TON >> I know, I know, the point I’m about to make is painfully ob­vi­ous. But it is not in any sense triv­ial: If you care who wins the elec­tion next month, get off the couch, go down to your polling place and vote.

Na­tional polls taken since last week’s de­bate show Hil­lary Clin­ton with a solid lead over Don­ald Trump; a Politico/Morn­ing Con­sult poll re­leased Mon­day morn­ing, for ex­am­ple, put the gap at 6 points. New polls in swing states, in­clud­ing some that once looked fa­vor­able for Trump, also re­port that Clin­ton is now ahead. There is ev­ery rea­son to be­lieve that most Amer­i­cans fa­vor the for­mer U.S. se­na­tor and sec­re­tary of state over the big­oted, clown­ish real es­tate mogul who claims he’s worth bil­lions of dol­lars yet ap­par­ently avoids pay­ing fed­eral in­come taxes.

If you’re tempted to think this is in the bag, how­ever, look around.

In Colombia on Sun­day, vot­ers nar­rowly re­jected a peace deal in­tended to end a war against left­ist guer­ril­las that has raged for five decades and claimed tens of thou­sands of lives. Sup­port­ers of the agree­ment were shocked be­cause re­spected polls had shown it would be ap­proved eas­ily.

Sim­i­larly, polls showed that Bri­tish vot­ers were in fa­vor of re­main­ing in the Euro­pean Union. Yet when bal­lots were counted af­ter the June 23 ref­er­en­dum, the “leave” po­si­tion had won a slim vic­tory. Many Bri­tons were stunned and dis­mayed — none more so than David Cameron, who was forced to re­sign as prime min­is­ter.

It is tempt­ing to look at these re­sults — plus the elec­tion of dan­ger­ous lu­natic Ro­drigo Duterte as pres­i­dent of the Philip­pines — and con­clude that some sort of vast, per­haps un­stop­pable, anti-elite wave is sweep­ing the globe. As go Medellin and Manila, in other words, so goes Mil­wau­kee.

I think there is a sim­pler, less apoc­a­lyp­tic ex­pla­na­tion: In both Bri­tain and Colombia, the out­comes were de­ter­mined by those who didn’t bother to vote.

For the Brexit ref­er­en­dum, over­all turnout was high, a bit over 70 per­cent. But turnout among vot­ers un­der 40 — those most likely to fa­vor re­main­ing in the EU — was only about 65 per­cent, ac­cord­ing to a Lon­don School of Eco­nom­ics anal­y­sis. Mean­while, turnout among those over 65, the group most likely to fa­vor ex­it­ing the union, was an es­ti­mated 90 per­cent.

Had turnout among younger vot­ers been a few points higher, Brexit would have lost.

In Colombia, a na­tion of 40 mil­lion peo­ple, the peace deal was re­jected by just 54,000 votes. But turnout was a pal­try 37 per­cent. If so many Colom­bians who fa­vored the agree­ment hadn’t as­sumed it was safe to stay home, be­liev­ing the out­come was a fore­gone con­clu­sion, Pres­i­dent Juan Manuel San­tos would be tak­ing a vic­tory lap in­stead of scram­bling to come up with a Plan B. The les­son for Amer­i­can vot­ers seems clear. Yes, this is a year when anti-es­tab­lish­ment protest is find­ing ex­pres­sion at the bal­lot box. The Duterte case is in­struc­tive: Filipino vot­ers knew they were choos­ing as pres­i­dent a man who be­lieves the way to deal with il­le­gal drugs and ram­pant crime is through ex­tra­ju­di­cial sum­mary ex­e­cu­tion. They may come to re­gret their choice, but they made it with open eyes.

In Bri­tain and Colombia, how­ever, ma­jori­ties of vot­ers sab­o­taged them­selves with their own ap­a­thy. And the only way Trump can win is if the same thing hap­pens here.

It is true that the white work­ing-class vot­ers who form the core of Trump’s sup­port do not al­ways show up on Elec­tion Day. But given their fer­vor for the bom­bas­tic GOP can­di­date — who claims, ridicu­lously, that he can hold back the tides of glob­al­ism, de­mog­ra­phy and sci­ence — it is rea­son­able to as­sume that Trump’s peo­ple will in­deed vote.

But they are out­num­bered, how­ever, by vot­ers who rec­og­nize Trump for the ig­no­rant and dan­ger­ous char­la­tan that he is. Poll­sters try to ac­count for any en­thu­si­asm gap when they screen for “likely” vot­ers. But re­ally there should be no gap at all.

The coali­tion of women, young peo­ple, African-Amer­i­cans, His­pan­ics and Asian-Amer­i­cans that twice elected Pres­i­dent Obama has even more rea­son to come out in force to elect Clin­ton. Any­one who be­lieves that Trump is es­sen­tially harm­less, or that he is so ridicu­lous a fig­ure that in­evitably he will lose, is whistling past the grave­yard.

The Clin­ton cam­paign is set­ting in mo­tion a get-out­the-vote cam­paign that rep­re­sents the state of the art. Ul­ti­mately, how­ever, this is on you. There is one sure way to avoid the nas­ti­est of surprises on Nov. 8: Vote, or you’ll have no right to com­plain.